DESCRIPTION (Investigator's Abstract): Much of the communication carried out by neurons in the central nervous system is mediated by neurotransmitter-gated ion channels. Elucidating how the structure of such neurotransmitter receptors relates to their function is important in understanding the basis for genetic and pathological variations in receptor functions and for designing therapeutic strategies. Molecular approaches for identifying nucleotide sequences that encode neurotransmitter receptors from the brain have demonstrated a host of variants of several neurotransmitter receptors whose functions have not been delineated. In contrast, much is known about the types of neurotransmitter receptors and the locations of neurons that bear various receptors in the nervous system of the marine mollusc, Aplysia californica. Application of the polymerase chain reaction (PCR) technique has led to the amplification of an acetylcholine receptor-like sequence from Aplysia. Use of this sequence as a molecular probe for in situ hybridization studies of wholemounts of Aplysia ganglia and identified Aplysia neurons in culture is proposed as one approach to identifying the type of receptor that this PCR fragment encodes. Culturing Aplysia neurons is included in this study since regenerating neurons will most likely contain enriched amounts of mRNA for producing receptor proteins. Two of the acetylcholine receptors (ACHRs) in Aplysia have pharmacological characteristics similar to the nicotinic receptors in vertebrate muscles and autonomic ganglia. However, the ion channels associated with the Aplysia ACHRs are quite different, one opens a C1- channel and another is selective for a Na+ channel. Thus, elucidation of the sequence encoding Aplysia ACHRs will provide insights to the parts of the sequence forming the ion channel and sites where various pharmacological agents bind. These studies will also increase our understanding of the evolutionary and perhaps combinatorial mechanisms that may be involved in generating the diversity of neurotransmitter receptors present in the central nervous system. Both undergraduate and graduate students will be involved in carrying out the proposed studies. In addition, the work proposed will introduce several important and powerful molecular techniques to our campus which is in the process of meeting the challenge of preparing our students for the technological revolution introduced by molecular biology.